Method for through-bulkhead shock initiation



R. c. ALLEN March 8, 1966 METHOD FOR THROUGH-BULKHEAD SHOCK INITIATIONFiled Oct. 8, 1963 mm mu WA C M R E B OW Y B m ATTORNEYS United StatesPatent Ofi ice 3,238,876 METHOD FOR THROUGH-BULKHEAD SHOCK INITIATIONRobert C. Allen, Hollister, Califi, assignor to McCormick SelphAssociates, Inc, Hollister, Califi, a corporation of California FiledOct. 8, 1963, Ser. No. 314,676 5 Claims. (Cl. 102-70) The presentapplication relates to a method for the exterior application of a highvelocity explosively gen erated shock wave to initiate a deflagration ordetonation on the interior of an intervening barrier without perforationthereof.

A contemporary problem in the aerospace industry is the initiation of ahigh velocity, explosively generated shock wave from the outside of anincompressible bulkhead to initiate a defiagration or detonation on theinside of the bulkhead while maintaining the integrity of the bulkhead.Numerous previous inventors have considered the problem ofthrough-bulkhead shock initiation. Several have discarded attempts toinitiate the required shock without perforation of the barrier. At leastone, Cushing, Patent No. 1,159,653, has relied on heat conductionthrough an intervening bulkhead to initiate an internal tracer charge.The present invention depends entirely on shock wave transmission toinitiate a pick-up charge within the interior of a bulkhead. The presentinvention consists in aligning donor and pick-up explosive chargesrespectively on the outside and the inside of the bulkhead beingattacked, positioning a detonating fuse adjacent the donor charge on theoutside of the bulkhead; sealing an ignition charge within the bulkheadadjacent the pick-up charge and detonating the detonating fuse and donorcharge so as to generate a high-velocity explosive shock wave whichinitiates the aligned pick-up and ignition charges Without perforatingthe intervening bulkhead. In turn the pick-up charge creates the desireddetonation or deflagration. In the ensuing description the termdetonation is used generically to comprehend also a deflagrationreaction.

Accordingly, it is an object of invention to provide a method forthrough-bulkhead shock initiation while maintaining the integrity of thebulkhead.

Another object of invention is to provide a throughbulkhead shockinitiation device which is simply designed and safely operable.

Yet additional objects of invention will become apparent from theensuing specification and attached drawings wherein FIG. 1 is aperspective view of a suggested throughbulkhead shock initiation devicecomprising a housing threaded for engagement with a bulkhead (notillustrated) and a detonating fuse coupling 14 insertable within thehousing.

FIG. 2 is a longitudinal section of the housing With detonating fusecoupled thereto;

FIG. 3 is a longitudinal section of a modified housing, having radialflanges for bolting to a bulkhead; and

FIG. 4 is a longitudinal section of another modification of invention.

In FIGS. 1 and 2, a suggested through-bulkhead shock 3,238,876 PatentedMar. 8, 1966 crystalline high explosive, such as pentaerythrite,tetranitrate (PETN) or cyclonite (RDX), which reacts with a velocity ofreaction in excess of 3,000 feet per second.

The purpose of donor explosive charge 22 is to generate a shock wave andby proper application to efiiciently transmit the shock wave into theintervening bulkhead material 56 between donor charge 22 and pick-upcharge or slug of inert material 24 without rupturing bulkhead material56.

It is suggested that the intervening material be relativelyincompressible, for example stainless steel, commercially manufacturedas Type 321 CRES. It is mandatory, of course, under the presentinvention, that the intervening material whether aluminum, steel,plastic, or other relatively incompressible material, be integral withthe main body of the housing 10.

Turning again to FIG. 2, housing 10 is illustrated as having threads 23provided to engage complementary threads within the bulkhead of anignition or like chamber.

Ignition charge 26 may be of a loose-grained type and may be sealed withrespect to the inside of the bulkhead by a stainless steel or likesealing 32 supported against the ignition charge by means of an annularrim 30.

In the FIG. 3 modification, annular rim 35 supports propellant trap 36which abuts stainless steel coined closure 32'. Grain propellant 70 issupported within inside end 58 and in turn at its forward end issupported by an inhibiting stainless steel washer 40.

The loose ignition charge 26 is axially elongated and extends fromthrust pick-up charge 24" being sealed at one end by coined closure 32and at the other end by stainless steel closure 50.

Ignition charge 26' is contained within a stainless steel spacer 48,fiber glass spacer 46, rubber-silicon ring 44, and retainer 42 theassembly of which attenuates the detonation output generated by thepick-up charge. Housing 10 may be provided with radially extendingflange 2% having longitudinal apertures 54 for bolting the entireassembly to a bulkhead. As in the modification suggested in FIG. 3, thedetonating fuse end closure 16' has a stainless steel closure 52adjacent the donor charge 22.

In the FIG. 4 modification interior threaded sleeve 60 is provided forsecurement of ignition charge 26 and a foraminous trap 62 is positionedintermediate ignition charge 26 and pick-up charge 24-. Wave spring 64may be fitted into quick-disconnect coupling 14 for a secure fitting ofcoupling 14- to housing 10'. Confined detonating fuse transfer line 12'may also include a soldered fitting 66 for retaining quick-disconnect14'. Confinement sleeve 68 may be supported at the end of detonatingfuse 12, and contains booster charge 69 to enhance and orient thereactive shock of fuse 12' towards donor charge 22'.

Manifestly, the invention is not restricted to the amount, type ormethod of application of the pick-up charge, except that the pick-upcharge shall be a meta-stable chemical composition capable of beinginitiated by the energy or" an explosively generated shock wave. Recenttests have proven that the suggested method of initiation can beaccomplished through 1.60 inches of solid steel without jeopardizingperformance reliability. Also, tests have proven that a .110 inch solidsteel bulkhead following through-bulkhead shock initiation according tothe present method will retain in excess of 50,000 p.s.i. differentialpressure without breaking.

The principal advantages of the present method over conventional methodsof shock initiation reside in the elimination of the need for drilling,tapping or otherwise disturbing the hermetic seal of containers,pressure vessels and pressure bulkheads, such as rocket engine cases toaccomplish ignition, detonation, or stimulus transfer. Also, theinvention eliminates the need for moving parts or electric wiringnormally utilized in conventional explosive detonators. Theh inventioneliminates, also, the need for primary explosive compositions normallyutilized in conventional explosive initiators thus removing the devicefrom the restricting shipping, storage and handling regulationsapplicable to primary high explosives.

Since the suggested initiator is non-electric and incorporatescontinuous conductive shielding around all explosive charges, theinitiator is completely insensitive to all R.F., stray currents, orother induced or even deliberately applied electrical energies. Theinitiator design simplicity renders the unit amendable to economic massproduction techniques. The initiator can be easily modified so thateither a deflagration for ignition, detonation, or mechanical motion canbe generated on the output or pick-up side by simply selecting aproperly designed adapter.

The utilization, within the initiator of the rapid and extremelyreproducible detonation shock wave phenome non provides initiationreproducibility and, when properly interconnected, simultaneity thatcannot be approached by conventional electric or mechanical initiators.The method of initiating the donor charge, on the input side of thebarrier, is not important to the invention and may utilize any of themeans, well known to the art including a blasting cap, mild detonatingfuse, Primacord type detonating fuse, exploding bridgewire and the like.

The type and quantity of the donor charge is not essential, of course,to the invention except that it is restricted to only those chemicalcompositions that react at a rate suflicient to generate a detonatingshock wave when properly initiated such as PETN, TNT and RDX.

Also, the type and thickness of the interveningbarrier is not criticalfor the purposes of the present invention. Metal barriers have been thesubject of all previous tests, but it is believed that certain plasticand/ or ceramic materials may accomplish the required action essentiallyas well as metal. Maintaining the integrity of the hermetic seal, formedby the barrier between the donor and pickup charges, before, during, andfollowing the detonating is the most critical aspect of the invention.

The type and quantity of pick-up charge is not intended to be essentialto the invention except that it must be of a material and form toaccomplish a useful function on receipt of the shock wave generated bythe donor charge at the barrier pick-up charge interface. Although onlyhigh explosive and a few deflagrating type pick-up charges have beenevaluated, it is visualized that any shock sensitive chemicalcomposition may be used as a pick-up charge. In fact, an inert movablepiece, such as a metal piston, can be impulsively loaded by the shockwave as it emerges from the barrier, and by moving and accomplishing auseful function, the inert piston, in such a case, can act as a pick-upcharge.

As indicated previously, the pick-up charge can be used to generate adetonation, deflagration, slow-burning, or simply mechanical movement.The essential characteristic of the donor and pick-up charges is thattheir combined explosive charge may be confined, positioned, orcontained in a manner that will not cause the hermetic barrier seal tobe broken or otherwise perforated.

Manifestly, various types of charges may be substituted and thesuggested housing may be differently configured without departing fromthe spirit and scope of the invention, as defined in the subjoinedclaims.

I claim:

1. A through-bulkhead detonation device comprising:

(a) a housing integrally supported within said bulkhead and havingcoaxially aligned donor and pick-up ports opening on either side of saidbulkhead, together with an intervening substantially non-compressibleportion interposed between said ports;

(b) a crystalline high-explosive donor charge from a group of secondaryhigh explosives consisting of pentaerythrite tetranitrate (PETN) andcyclonite (RDX) which react with a velocity in excess of 3,000 feet persecond positioned at the base of said donor port adjacent saidnon-compressible intervening portion;

(0) a secondary high-explosive pick-up charge capable of being initiatedby the energy of an explosively generated shock wave positioned at thebase of said pick-up port adjacent said intervening non-compressibleportion; and

(d) an ignition charge supported adjacent said pickup charge inside ofsaid bulkhead.

2. A through-bulkhead detonation device as in claim 1, said pick-up anddonor charges being sealed against said housing and said interveningbulkhead portion by stainless steel closure means.

3. A through-bulkhead detonation device as in claim 1, said housingincluding a radially extending medial flange with longitudinal aperturesfor securement of said flange to a bulkhead of a chamber into which theshock is being conveyed.

4. Method for through bulkhead initiation of detonation comprising:

(a) confining a donor explosive charge adjacent the outside of abulkhead being attached;

(b) confining a pick-up explosive charge adjacent the inside of saidbulkhead and in axial alignment with said donor charge so that anintervening portion of said bulkhead remains between said donor chargeand said pick-up charge;

(0) limiting the combined explosive of said donor and pickup charges soas to avoid perforating and deforming said bulkhead;

(d) sealing an ignition charge within the inside of said bulkheadadjacent said pick-up charge; and

(e) detonating said donor charge so as to generate a high velocity shockwave which initiates said aligned pick-up charge and ignition chargewithout perforating and deforming said bulkhead.

5. Method as in claim 4, wherein said donor explosive charge is acrystalling high explosive from a group consisting of pentaerythritetetranitrate (PETN) and cyclonite (RDX) which reacts with velocity inexcess of 3,000 feet per second.

References Cited by the Examiner UNITED STATES PATENTS 2,402,235 6/1946Burrows et a1. 10229 X 2,833,213 5/1958 Udry 10220 2,948,219 8/1960 Sapp102--27 X 3,045,524 7/1962 Stresau et al 10270 X 3,106,892 10/1963Miller 10227 3,129,663 4/ 1964 Schnepfe 102-27 3,159,103 12/1964 Bagley10270 X 3,162,127 12/1964 Breslow et al 102-865 X FOREIGN PATENTS911,587 11/1962 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner.

G. L. PETERSON, G. H. GLANZMAN,

Assistant Examiners.

1. A THROUGH-BULKHEAD DETONATION DEVICE COMPRISING: (A) A HOUSINGINTEGRALLY SUPPORTED WITHIN SAID BULKHEAD AND HAVING COAXIALLY ALIGNEDDONOR AND PICK-UP PORTS OPENING ON EITHER SIDE OF SAID BULKHEAD,TOGETHER WITH AN INTERVENTING SUBSTANTIALLY NON-COMPRESSIBLE PORTIONINTERPOSED BETWEEN SAID PORTS; (B) A CRYSTALLINE HIGH-EXPLOSIVE DONORCHARGE FROM A GROUP OF SECONDARY HIGH EXPLOSIVES CONSISTING OFPENTAERYTHRITE TETRANITRATE (PETN) AND CYCLONITE (RDX) WHICH REACT WITHA VELOCITY IN EXCESS OF 3,000 FEET PER SECOND POSITIONED AT THE BASE OFSAID DONOR PORT ADJACENT SAID NON-COMPRESSIBLE INTERVENTING PORTION; (C)A SECONDARY HIGH-EXPLOSIVE PICK-UP CHARGE CAPABLE OF BEING INITIATED BYTHE ENERGY OF AN EXPLOSIVELY GENERATED SHOCK WAVE POSITIONED AT THE BASEOF SAID PICK-UP PORT ADJACENT SAID INTERVENING NON-COMPRESSIBLE PORTION;AND (D) AN IGNITION CHARGE SUPPORTED ADJACENT SAID PICKUP CHARGE INSIDEOF SAID BULKHEAD.